It was recognized for many decades that using oxygen-enriched air in fossil-fueled combustion engines can lead to significant benefits, such as increasing in power output, improving fuel consumption (conversion efficiency) and thermal conversion efficiency, and reducing exhaust emissions of carbon monoxide and hydrocarbons. Substantial efforts have been aimed at improving engine efficiencies and decreasing emissions that pollute the environment, using, for example, permeable membranes, to provide the oxygen-enriched. Notwithstanding the advantages of introducing the oxygen-enriched air in various fossil-fueled combustion devices/systems, the lack of an economical source of on-line oxygen has made it difficult to provide a practical application of the concept of providing the oxygen-enriched air to corresponding engines/systems, at least during various phases or time periods of operation of the engine.